The present invention relates to the field of angioplasty and in particular, to new and improved catheters for performing balloon angioplasty procedures on blood vessels.
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating vascular diseases. Percutaneous transluminal angioplasty is widely used for the treatment of stenosis within the coronary arteries, and has been used for the treatment of stenosis in other areas of the vascular system.
The most widely used method of percutaneous transluminal angioplasty makes use of a dilatation catheter which has an inflatable balloon member at a distal end and an inner core containing a guide wire. The guide wire is threaded through the vascular system by tracking radiopaque coils contained at a distal tip which are monitored on an x-ray fluoroscope. Once the guide wire is positioned across the stenosis requiring treatment, the balloon member is advanced over the guide wire and positioned in the stenosis. The balloon member is subsequently inflated with liquid via an inflation lumen to exert pressure radially and outwardly against the lesion, causing the artery wall to stretch and reestablishing an acceptable blood flow through the artery.
Any air or other gases within the catheter must be purged before the catheter is introduced into the patient. One means for accomplishing this, as illustrated in U.S. Pat. No. 4,323,071, (Simpson, et al), is by incorporating a vent tube to direct the air and other gases proximally from the distensible balloon portion through the catheter so that the air or other gases are released outside the catheter at a proximal end thereof. A purging medium is introduced into the catheter whereby the air or other gases trapped within the balloon member are forced out through the vent tube. U.S. Pat. No. 4,715,378, (Pope, Jr., et al), discloses a gas purging arrangement where a catheter allows purging of air trapped within the balloon member by providing air passages in the windings of a coil located at the distal end of the catheter. U.S Pat. No. 4,821,722, (Miller et al), shows a catheter purging design wherein holes in the balloon member wall or in an interior surface of the inflation lumen allow the passage of air but are so small that the passage of inflation liquid therethrouqh is restricted.
The catheter purging arrangements described above have several disadvantages. One disadvantage is that it is often difficult to assure that all of the air trapped within the balloon catheter has been released. Furthermore, a larger profile catheter shaft is often required (e.g., to accommodate a purge tube) and the purging steps are often time consuming. Other disadvantages include difficulty in manufacture, high manufacturing expense and quality control. Therefore, there is a continuing need to provide an inexpensive balloon catheter that incorporates a quick and reliable method of purging the catheter of air.